These delicate convex glass discs very likely served as covers for clock faces. They are antique, made by Leo Popper & Sons, a glass company that operated for 91 years as manufacturers, importers, wholesalers and distributors of glass articles. According to www.glassian.org, it was Popper who supplied the glass for the Statue of Liberty's replacement torch (damaged in the Black Tom explosion in 1916). You can find a great essay on the history of Leo Popper & Sons on the Glassian website here.
When Leo Popper & Sons finally closed in 1971, Whittemore-Durgin bought their stock on hand, and some of their unusual items are still in stock at W-D today.
These unique clock covers have a thin beveled edge, and can be used like a rondel in your stained glass work with foil or lead. You could sandwich some of our pressed flowers, or some thin and delicate ephemera, in between two of these thin discs and then wrap the whole thing in foil. Or try etching the glass using one of our large supply of etching stencils. We'd love to see what you end up doing with them!
Package of 6.